NASSAU, Bahamas — John Travolta frantically gave mouth-to-mouth resuscitation to his dying son, and then desperately wanted to fly him to Florida in a last-ditch bid to save the teen’s life, the actor said today.

The “Pulp Fiction” actor is the star witness in the sensational prosecution of an ambulance driver and former senator accused of extorting Travolta days after Jett Travolta, 16, died earlier on Jan. 2 in the Bahamas.

Travolta’s testimony marked his first public comments about Jett’s death. The heartbroken dad described the panic and horror that erupted inside his vacation home after Jett was found unconscious in the bathroom.

The somber actor kept his composure on the witness stand, never crying or letting his voice crack. He described how ER doctors in the Bahamas unsuccessfully tried to revive Jett before the actor realized: “No, he was not alive.”

Travolta’s heart-wrenching words prompted wife and actress Kelly Preston to grab a bundle of tissues and wipe away her tears.

Travolta’s testimony is expected to continue tomorrow.

Before court closed today, a frustrated Travolta told jurors it took “35 minutes, 40, something in that area,” for the ambulance to arrive at his vacation home.

The slow response and Jett’s dire condition led Travolta to ask the ambulance driver to take them to the airport.

“Yes, to take my son on a [private jet] to West Palm Beach because it was quicker than taking him to the Freeport hospital,” the actor to rapt jurors.

That’s when Travolta signed a document, holding paramedics harmless for not taking Jett to the hospital, he said.

Travolta told prosecutor Bernard Turner he knew what he was signing but didn’t read all the papers: “Because time was of the essence.”

Former Bahamian Sen. Pleasant Bridgewater and ambulance driver Tarino Lightbourne have pleaded not guilty to extortion charges. They allegedly wanted Travolta to pay them $25 million to keep the hold-harmless documents secret.

Travolta, an avid aviator, initially believed he could get Jett to ER doctors faster by taking him to Florida, before changing his mind and opting for the local hostpital.

The actor described Jett’s autism and said the disorder was such a huge burden that few days ever passed without a scary seizure. Authorities ruled that Jett died because of a seizure

“Yes, my son was autistic and he suffered from seizure disorder,” Travolta said.

“Every five to 10 days, he would suffer seizures that would last 45 seconds to a minute, and then he would sleep for 13 hours.”

Travolta testified he was sleeping next to wife Preston when a nanny pounded on his door just after Jett was found unconscious.

“I ran down stairs to help my son with my wife to my son’s bedroom,” Travolta told the jury of six women and three men. “I saw he [Jett] was on the bathroom floor.”

Travolta said he jumped into action as soon as he saw others working to save his son.

“His other nanny Jeff Kathrein and an employee for [the resort] were doing CPR,” said Travolta. “I took the place of the woman doing CPR.

“Jeff Kathrein who is his other nanny was doing compression, I was doing breathing and I had asked if an ambulance had been called and they said ‘yes,’ an ambulance had been called.”

Travolta — wearing a black suit, white shirt and silver tie — entered court holding hands with Preston, who was in a navy blue dress. They were surrounded by an entourage of the supercouple’s lawyers.